Triaziridine. 8. On the Acylation of Dialkyl-triaziridines

Article abstract of DOI:10.1002/hlca.19870700217

(2,3-trans)-Diisopropyl- (1) and (2,3-cis)-1,3-cyclopentylenetriaziridine (2) were reacted with ClCOOCH3.In the case of 1, with or without pyridine, an expected acylation at N(1) resulted in the methoxycarbonyl derivative 3.In the case of 2, the reaction in pyridine led to the γ- and α-dihydropyridyl derivatives 5 and 6, respectively, where the acylpyridinium moiety had become attached by a ring C-atom to N(1); without pyridine, it afforded the N-cyclopentenylcarbamates 13 and 14 by opening of the triaziridine ring and loss of N₂.The mechanisms proposed for these reactions involve the initial attack of an electrophile at N(1) of 1 but at N(2) (or N(3)) of 2.This difference is rationalized with steric factors, inasmuch as the hindrance to an attack at N(2) (or N(3)) is greater in 1 than in 2, whereas this hindrance at N(1) is smaller in 1 than in 2.The greater resistance to opening of the saturated N₃-homocycle during acylation of the monocyclic triaziridine 1, as compared to that of the tricyclic one 2, is attributed to greater strain in the latter system.